Definition of Unsaturated

not saturated; capable of dissolving more of a substance at a given temperature;

Capable of taking up, or of uniting with, certain other elements or compounds, without the elimination of any side product; thus, aldehyde, ethylene, and ammonia are unsaturated; benzene has three unsaturated bonds. The term is applied most commonly to compounds with a double or triple bond between two carbon atoms (as in ethylene).